Keyboard shortcut for texture paint brush strength?
Use Shift+F for Strength, F for Radius, and Ctrl+F for rotation of brush texture. 

When using a brush texture in Stencil mode, RMB to move, Shift+RMB to scale, and Ctrl+RMB to rotate the stencil image. 

When using Stencil in Brush Mask, Alt+RMB to move, Shift+Alt+RMB to scale, and Ctrl+Alt+RMB to rotate. 

I use these all day, and prefer them to the typical  [ and ] usage in photoshop and other editors.